Mobile X-ray devices in the form of C-arm devices are used, for example, for intraoperative imaging in operational deployment. The devices are positioned precisely in relation to the patient to be treated prior to each deployment. The devices may be equipped with wheels, on which the devices may be displaced manually. The wheels may be driven in a motorized manner to enable the displacement of the devices with less or without any exertion of force and to automate movements of the devices for clinical applications.
A C-arm system with three wheels is known from U.S. Pat. No. 6,374,937 B1, where two of the wheels are each connected to a drive and are mounted such that the wheels may be pivoted about a vertical axis. A third wheel is implemented in a freely movable manner. Using the driven wheels, a movement of the C-arm system along a direction (e.g., in parallel with a patient couch) may be controlled. The pivoting of the wheels about the vertical axis is possible between a first and a second position. The drives of the wheels are arranged in a base unit or a lower chassis of the C-arm system.
Similar C-arm systems are known from U.S. Pat. No. 8,666,582 B2, U.S. Pat. No. 8,177,430 B2 and EP 1 246 566 B1.
A frequently recurring problem in clinical applications is adopting directions of movement with the mobile C-arm system (e.g., a movement in the opposite direction). Examples include when the C-arm system is moved backwards, to the side, or diagonally away from the examination couch, or to create space for an operating surgeon. Subsequently, the C-arm system may be reversed into an original position on the examination couch again. In the “park & return” example, the mobility and the steering of the wheels are implemented so that a precise reversal of the previous movement is possible.
Another example is “stitching” (e.g., when a panoramic recording of the patient is to be compiled). The C-arm is first moved by the user along the patient couch without imaging to avoid collisions in the actual operating mode and to define the start and end point of the recording. For the panoramic recording, the movement of the C-arm in the precise opposite direction is performed. The steering of the wheels is implemented such that a precise reversal of the previous direction is possible.
A further example includes a C-arm system without isocentric geometry. The object to be imaged is kept in the center of the image during a change in the orbital angle that is possible by a change in the lifting column position and the wheel position. During a constant shift in the imaging position, the orientation of the wheels of the C-arm system are held precisely to provide a precisely equal movement in the opposite direction.